2024 Volume 83 Issue 1 Pages 23-32
A 37-year-old woman with hereditary Parkinson’s disease (PARK2: exon 3/7 hetero-duplication & exon 3/5 hetero-deletion) visited our neuro-otology unit for evaluation of postural instability; she had no history of dizziness or vertigo. Neurological examination revealed no other significant abnormalities than the cardinal signs of Parkinsonism: mild rigidity, resting tremor and dystonia. Brain MRI revealed mild atrophy of the cerebellar dorsal vermis and hemisphere. The ENG showed square wave jerks (SWJ) during forward gaze in the dark. The visually guided saccades were hypometric in both the horizontal and vertical directions. Both horizontal and vertical smooth pursuits were slightly disturbed and required corrective anticipated saccades to follow the sinusoidal target. Horizontal OKN could be induced, but the slow phase velocity and frequency were relatively reduced. These findings were slightly different from those in sporadic Parkinson’s disease, although there were also some similarities. Considered with the MRI findings, the above ENG findings suggest dysfunction of not only the basal ganglia, but also of the cerebellum, especially the vestibular cerebellum, including the dorsal vermis, fastigial nucleus, flocculus, and ventral paraflocculus. In conclusion, it is necessary to consider dysfunction of the cerebellum, as also that of the basal ganglia, as the cause of the abnormal eye movements in this case.
